Host device and slave device controlling method

ABSTRACT

A host device is provided, which includes a network communication unit connected to network; a local communication unit locally connected to a slave device; a virtualization unit to virtualize the slave device as a network device within the network; and a controlling unit to control the virtualized slave device as the network device. Therefore, a developer may implement an application in consideration of a single type of network without considering various physical input and output ports.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of Korean Patent Application No.2009-76287, filed in the Korean Intellectual Property Office on Aug. 18,2009, the disclosure of which is incorporated herein by reference.

BACKGROUND

1. Field

Aspects of the present invention relate to a host device and a slavedevice controlling method, and more particularly, to a host device whichvirtualizes a slave device connected to the host device locally andcontrols the slave device in a method of controlling a network deviceand a slave device controlling method.

2. Description of the Related Art

Generally, a host device is connected to a slave device through variousconnection channels such as a serial, a universal serial bus (USB), andEthernet, and provides a user with various applications through theslave device being connected to the host device.

Applications provided from a host device should be implemented to complywith physical characteristics of the slave device connected to the hostdevice and various communication protocols on the physical layer.

Accordingly, the developer of applications of a host device needs todevelop applications that comply with driver software for the connectionof various physical layers on the host device and various communicationprotocols that exist beyond the physical layers.

However, a developer has difficulty in implementing applications becausethe developer should consider various physical input and output portssince the recent host devices are capable of being connected to varioustypes of slave devices. In addition, the host devices have poorcompatibility between applications which drive different types of slavedevices.

SUMMARY

Aspects of the present embodiment relate to a host device whichvirtualizes a slave device connected to the host device via a local loopand controls the slave device in a method of controlling a networkdevice and a slave device controlling method.

Additional aspects and/or advantages will be set forth in part in thedescription which follows and, in part, will be apparent from thedescription, or may be learned by practice of the invention.

The foregoing and/or other aspects are achieved by providing a hostdevice, including a network communication unit connected to a network; alocal communication unit locally connected to a slave device; avirtualization unit to virtualize the slave device as a network devicewithin the network; and a controlling unit to control the virtualizedslave device as the network device.

The virtualization unit may include a determination unit to identify acommunication protocol of the slave device; a message conversion unit toconvert a message of the controlling unit and a message of the slavedevice into a message which complies with a communication protocol ofthe slave device and a message which complies with a communicationprotocol of the network device, respectively, according to theidentified communication protocol; and a message transmission unit totransmit the message converted by the message conversion unit to adestination of the message.

The message conversion unit may analyze the message of the controllingunit and the message of the slave device and convert the messages tocorrespond to the analyzed result.

The virtualization unit may further include an Internet Protocol (IP)address generation unit to allocate an IP address to the slave devicewhen the slave device is connected to the host device.

When the message of the slave device is received from an externalnetwork device connected to the network, the controlling unit maycontrol the virtualization unit to convert the received message into amessage which complies with the communication protocol of the slavedevice and transmit the converted message to the slave device.

The message transmission unit may control the network communication unitto transmit the converted message of the slave device to the externalnetwork device.

The communication protocol of the network device may be a universalplug-and-play (UPnP) communication protocol.

The slave device may be connected to the host device in at least one ofa universal serial bus (USB) communication protocol, an IEEE 1394communication protocol, a Serial Peripheral Interface (SPI)communication protocol, and a High-Definition Multimedia Interface(HDMI) communication protocol.

The foregoing and/or other aspects are achieved by providing a method tocontrol a slave device locally connected to a host device via network,the slave device controlling method including virtualizing the slavedevice as a network device within the network; and controlling thevirtualized slave device as the network device.

The virtualizing may include allocating an IP address to the slavedevice when the slave device is connected to the host device; andidentifying a communication protocol of the slave device.

The controlling may include converting a message of the host device anda message of the slave device into a message which complies with acommunication protocol of the slave device and a message which complieswith a communication protocol of the network device, respectively,according to the identified communication protocol; and transmitting theconverted message to a destination of the message.

The converting may analyze the message of the host device and themessage of the slave device and convert the messages to correspond tothe analyzed result.

When the message of the slave device is received from an externalnetwork device connected to the network, the controlling may convert thereceived message into a message which complies with the communicationprotocol of the slave device and transmit the converted message to theslave device.

The controlling may transmit the converted message of the slave deviceto the external network device.

The communication protocol of the network device may be a universalplug-and-play (UPnP) communication protocol.

The slave device may be connected to the host device in at least one ofa universal serial bus (USB) communication protocol, an IEEE 1394communication protocol, a Serial Peripheral Interface (SPI)communication protocol, and a High-Definition Multimedia Interface(HDMI) communication protocol.

The foregoing and/or other aspects are achieved by providing a slavedevice controlling method, including: converting a message at a hostdevice connected to the slave device via a network from a firstcommunication protocol to a second communication protocol so that theslave device is virtualized as a network device of the network.

The first communication protocol may be a communication protocol of thenetwork device and the second communication protocol may be acommunication protocol of the slave device, and the message may beconverted from the first communication protocol of the network deviceinto the second communication protocol of the slave device andtransmitted to the slave device.

The first communication protocol may be a communication protocol of theslave device and the second communication protocol may be acommunication protocol of the network device, and the message may bereceived from the slave device and converted from the firstcommunication protocol of the slave device into the second communicationprotocol of the network device.

The host device may receive the message from an external network device,convert the message from a first communication protocol of the externalnetwork device into a second communication protocol of the slave deviceand transmit the converted message to the slave device.

BRIEF DESCRIPTION OF THE DRAWINGS

These and/or other aspects and advantages will become apparent and morereadily appreciated from the following description of the embodiments,taken in conjunction with the accompanying drawings, of which:

FIG. 1 is a block diagram of a host device according to an exemplaryembodiment;

FIGS. 2 to 5 are views provided to explain a virtualization of a hostdevice; and

FIG. 6 is a flowchart of the process of controlling a slave deviceaccording to an exemplary embodiment.

DETAILED DESCRIPTION

Reference will now be made in detail to the exemplary embodiments,examples of which are illustrated in the accompanying drawings, whereinlike reference numerals refer to like elements throughout. Theembodiments are described below, in order to explain the presentinvention by referring to the figures.

FIG. 1 is a block diagram of a host device according to an exemplaryembodiment.

Referring to FIG. 1, the host device 100 includes a user interface 110,a storage unit 120, a network communication unit 130, a localcommunication unit 140, a virtualization unit 150, and a controllingunit 160. The host device 100 may provide a user with an application(service), and may be a personal computer (PC), a laptop computer, atelevision (TV), or a set-top box (STB), for example.

The user interface 110 includes a plurality of function keys so that auser may set or select various functions supported by the host device100, and may display various information provided by the host device100. The user interface 110 may be configured with a device, such as atouch pad, which simultaneously executes input and output operations, ora device combining a mouse with a monitor, for example. Accordingly, auser may use various application services supported by the host device100 through the user interface 110.

The storage unit 120 may store content corresponding to various servicessupported by the host device 100, and protocol information of a slavedevice 200 which will be described later and an Internet Protocol (IP)address for the slave device 200. The storage unit 120 may be aninternal storage medium of the host device 100, or an external storagemedium, for example, a removable disk including a USB memory, a storagemedium being connected to a host, and a web server over a network.

The network communication unit 130 may be connected to a network. Inmore detail, the network communication unit 130 may be connected to anexternal network device 300 via the network, and transceive a message toand from the external network device 300 according to a communicationprotocol of the external network device 300. The network communicationunit 130 may be connected to the network by any suitable type of wiredor wireless link. In this exemplary embodiment, the communicationprotocol of the network device may be a universal plug-and-play (UPnP)communication protocol, and the external network device 300 is anotherhost device connected to the network which transceives a message to andfrom the host device 100 according to a network communication protocol.

Herein, the message may include various controlling commands between thehost device 100, the slave device 200, and the network device 300, and aresponse signal for the controlling commands, and may be, for example, aservice request, a state request, and a service providing signal inresponse to a service request.

The local communication unit 140 is connected to the slave device 200via a local loop. Specifically, the local communication unit 140 isconnected to the slave device 200 via a local loop, and transceives amessage to and from the slave device 200 according to a communicationprotocol of the slave device 200. For example, if the slave device 200is a USB device, the local communication unit 140 may transceive amessage to and from the USB device according to a USB communicationprotocol, and if the slave device 200 is an Institute of Electrical andElectronics Engineers (IEEE) 1394 device, the local communication unit140 may transceive a message to and from the IEEE 1394 device accordingto an IEEE 1394 communication protocol. The communication protocol ofthe slave device 200 may include a USB communication protocol, an IEEE1394 communication protocol, a High-Definition Multimedia Interface(HDMI) communication protocol, a serial communication protocol, and aparallel communication protocol, for example. In this exemplaryembodiment, the slave device 200 may be directly connected to the hostdevice 100 according to at least one of a USB communication protocol, anIEEE 1394 communication protocol, a Serial Peripheral Interface (SPI)communication protocol, and a HDMI communication protocol, for example,to provide a user with a service.

The virtualization unit 150 virtualizes the slave device 200 as anetwork device within the network. In more detail, the virtualizationunit 150 includes a determination unit 151, a message conversion unit152, a message transmission unit 153, and an Internet Protocol (IP)address generation unit 154. The virtualization allows the slave device200 to operate like a network device connected to the network bygenerating a virtual network device.

The determination unit 151 may determine a communication protocol of theslave device 200. Specifically, the determination unit 151 may recognizeinformation required to communicate with the slave device 200, such asthe type of the slave device 200 and the communication protocol. Forexample, if the slave device 200 connected to the host device 100 is aUSB memory, the determination unit 151 may recognize that thecorresponding slave device is a USB memory that communicates with thehost device 100 according to a USB communication protocol, using a PnPcommunication protocol. In addition, the determination unit 151 maystore the recognized information regarding the slave device 200 in thestorage unit 120.

The message conversion unit 152 may convert the message of thecontrolling unit 160 and the message of the slave device 200 into amessage which complies with the communication protocol of the slavedevice 200 and a message which complies with the communication protocolof the network device, respectively, according to the identifiedcommunication protocol of the slave device 200. Specifically, themessage conversion unit 152 may convert the message of the slave device200 into a message which complies with the communication protocol of thenetwork device, and convert the message of the controlling unit 160 orthe message of the external network device 300 into a message whichcomplies with the communication protocol of the slave device 200.

The message conversion unit 152 may analyze the message of thecontrolling unit 160 and the message of the slave device 200, andconvert the messages into messages corresponding to the analyzed result.In more detail, the message conversion unit 152 may analyze the messagesbetween the slave device 200 and the host device 100 as well as thecommunication protocol of the slave device 200 and the communicationprotocol of the network device, and convert the messages into messagescorresponding to the analyzed result. An algorithm or a look-up tablerelated to the analysis of the messages may be stored in the storageunit 120. Accordingly, a developer may develop an application withoutconsidering a message standardization of the slave device 200. Forexample, if Message 1 indicates a power-off operation of the slavedevice 200, the message conversion unit 152 interprets the messageindicating the power-off operation of the slave device 200 as Message 1using the pre-stored algorithm or look-up table, and converts Message 1into a message complying with the communication protocol of the slavedevice 200. On the other hand, if Message 1 is received from the slavedevice 200, the message conversion unit 152 analyzes Message 1 as themessage indicating the power-off operation of the slave device 200 usingthe pre-stored algorithm or look-up table, and converts the messageindicating the power-off operation into a message complying with thecommunication protocol of the network device.

The message transmission unit 153 may transmit the message which isconverted by the message conversion unit 152 to the destination of themessage. Specifically, the message transmission unit 153 may transmitthe message, which is converted by the message conversion unit 152 to besuitable for the destination of the message transmitted to thevirtualization unit 150, to the controlling unit 160 or the slave device200. For example, if the virtualization unit 150 receives a message tobe transmitted to the slave device 200 from the controlling unit 160,the message transmission unit 153 may control the local communicationunit 140 to transmit the message which is converted by the messageconversion unit 152 to the slave device 200. On the other hand, if thevirtualization unit 150 receives a message to be transmitted to thecontrolling unit 160 from the slave device 200, the message transmissionunit 153 may transmit the message which is converted by the messageconversion unit 152 to the controlling unit 160.

If the message of the slave device 200 to respond to the request of theexternal network device 300 is input to the virtualization unit 150, themessage transmission unit 153 may control the network communication unit130 to transmit the message which is converted by the message conversionunit 152 to the external network device 300.

The IP address generation unit 154 may allocate an IP address to theslave device 200 if the slave device 200 is connected to the host device100. Specifically, if the slave device 200 is connected to the hostdevice 100, the IP address generation unit 154 may allocate an IPaddress for the slave device 200 connected to the host device 100 usingan IP address for the host device 100. For example, if the IP address ofthe host device 100 is 127.0.0.1, the IP address generation unit 154 mayallocate the IP address for the slave device 200 to be 127.0.0.1:0002.In this situation, the IP address generation unit 154 may generate an IPaddress for the slave device 200 connected to the host device 100 bysearching for an available port of the host device 100.

The IP address generation unit 154 may store an IP address which isallocated to the slave device 200 in the storage unit 120. The IPaddress generation unit 154 may be implemented so that the same IPaddress is allocated to the slave device 200 which is repeatedlyconnected to the host device 100, or different IP addresses areallocated to the slave device 200 whenever the slave device is connectedto the host device 100. The above operation of the IP address generationunit 154 may be performed when a user commands the virtualization forthe slave device 200 or at the same time the slave device 200 isconnected to the host device 100.

The controlling unit 160 may control the virtualized slave device 200 byapplying the method of controlling the network device. In more detail,if the controlling unit 160 transmits a message to control thevirtualized slave device 200, the controlling unit 160 may generate amessage to comply with the communication protocol of the network device.The controlling unit 160 transmits the generated message complying withthe communication protocol of the network device to the virtualizationunit 150 and controls the virtualization unit 150 so that the message isconverted to comply with the communication protocol of the slave device200 and the converted message is transmitted to the slave device 200. Ifthe host device 100 receives a response message from the slave device200, the controlling unit 160 controls the virtualization unit 150 sothat the message received through the local communication unit 140 isconverted to comply with the communication protocol of the networkdevice and thus the converted message is used to perform a service.Herein, the method of controlling the network device refers to a methodof controlling a message between devices connected to a network, thatis, the method of communicating between network devices using UPnPcommunication protocol.

If the message for the slave device 200 is received from the externalnetwork device 300 connected to the network, the controlling unit 160may control the virtualization unit 150 to convert the message into amessage which complies with the communication protocol of the slavedevice 200 and transmit the converted message to the slave device 200since the received message complies with the communication protocol ofthe network device 300. If a response message is received from the slavedevice 200, the controlling unit 160 may control the virtualization unit150 so that the message is converted to comply with the communicationprotocol of the network device 300 and thus the converted message istransmitted to the external network device 300.

As described above, since the host device 100 virtualizes the slavedevice 200 connected to the host device 100 as a network device and thuscontrols the slave device 200 in the network device controlling method,a developer may develop an application in consideration of only a singlephysical connection. In addition, since the slave device 200 connectedto the host device 100 operates as a network device, the externalnetwork device 300 may easily control the slave device 200 connected tothe host device 100.

The single slave device 200 is connected to the host device 100 in FIG.1, but a plurality of slave devices may be connected to the host device100 and a plurality of network devices may also be connected to the hostdevice 100 via the network.

FIGS. 2 to 5 are views provided to explain a virtualization of a hostdevice according to an exemplary embodiment.

FIG. 2 illustrates the connection relationship between the host device100, the slave device 200, and the external network device 300 beforethe virtualization operation is performed. Specifically, the host device100 is connected to a cradle 230, an accessory device 220 in a serialcommunication manner, and is connected to a specific device 260, a USBmemory disk 210, a USB digital camera 240, and a USB camcorder (CAM)250, for example, in a USB manner. The host device 100 is connected toan electric display 310, a printer 320, and a hand phone 330, forexample, via a network. In this exemplary embodiment, the USB memorydisk 210, the accessory device 220, the cradle 230, the USB digitalcamera 240, the USB CAM 250, and the specific device 260 are exemplarydevices of the slave device 200, and the electric display 310, theprinter 320, and the hand phone 330 are exemplary devices of theexternal network device 300.

FIG. 3 illustrates the connection relationship between the host device100, the slave device 200, and the external network device 300 after thevirtualization operation is performed for the slave device 200.Specifically, the physical connection relationship between the devicesis identical to that of FIG. 2, but the slave devices 210 to 260 arevirtualized as a network device having each an IP address. Specifically,the cradle 230 connected to the host device 100 in a serialcommunication manner is virtualized as a network device 360 having IPaddress ‘127.0.0.1:0003,’ and the USB cam 240 connected to the hostdevice 100 in a USB manner is virtualized as a network device 380 havingIP address ‘127.0.0.1:0005.’ The accessory device 220, the specificdevice 260, the USB memory disk 210, and the USB digital camera 240 mayalso be virtualized as a network device 350, 390, 340, and 370,respectively.

The slave device 200 is connected to the host device 100 in a serialcommunication manner and a USB manner in FIGS. 2 and 3, but the slavedevice 200 connected to the host device 100 via other local loops mayalso be virtualized.

FIG. 4 is a view provided to explain a controlling method of the hostdevice 100 when a slave device is virtualized.

Referring to FIG. 4, a slave device 220 is physically connected to thehost device 100 via a local loop, but if the slave device 220 isvirtualized, the host device 100 may control a virtualized slave device350 in a method of controlling a network device. In addition, since theslave device 220 is virtualized as a network device 350, the hand phone330, which is an external network device, may easily control thevirtualized slave device 350.

That is, the host device 100 and the external network device 300connected each other via a network constitute a home network before theslave device 200 is virtualized as shown in FIG. 5, but the slave device200 connected to the host device 100 is also an element whichconstitutes a home network after the slave device 200 is virtualized.Accordingly, the external network device 300 may easily control theslave device 200.

FIG. 6 is a flowchart of the process of controlling a slave deviceaccording to an exemplary embodiment.

Referring to FIG. 6, a slave device may be virtualized as a networkdevice within network. Specifically, if the slave device is connected toa host device, an IP address is allocated to the slave device inoperation 610, and the communication protocol of the slave deviceconnected to the host device may be identified in operation 620. In moredetail, if the slave device is connected to the host device, an IPaddress may be allocated to the slave device connected to the hostdevice using an IP address of the host device. In this situation, an IPaddress for the slave device connected to the host device may begenerated by searching for an available port of the host device. Thetype of slave device connected to the host device and the communicationprotocol of the slave device may be identified using a PnP communicationprotocol. An IP address allocated to the slave device, the type of theslave device, and the communication protocol of the slave device may bepre-stored, and may also be used in subsequent operations. The operationof allocating an IP address and the operation of identifying thecommunication protocol of the slave device may be performed in reverseorder.

The virtualized slave device may be controlled in a method ofcontrolling a network device. Specifically, a message of the host deviceand a message of the slave device are converted to comply with thecommunication protocol of the slave device and the communicationprotocol of the network device, respectively, according to theidentified communication protocol of the slave device in operation 630.The converted messages are transmitted to the corresponding destinationsin operation 640. For example, if the host device transmits a messageindicating the command of controlling the virtualized slave device tocomply with the communication protocol of the network device, the hostdevice converts the message complying with the communication protocol ofthe network device into a message complying with the communicationprotocol of the slave device and transmits the converted message to theslave device. If the host device receives a response message from theslave device, the host device converts the response message into amessage complying with the communication protocol of the network devicesince the message on the slave device complies with the communicationprotocol of the slave device, and the host device uses the convertedmessage.

If the host device receives the message of the slave device from anexternal network device connected to the host device via a network, thehost device converts the received message to comply with thecommunication protocol of the slave device since the received messagecomplies with the communication protocol of the network device, andtransmits the converted message to the slave device. If the host devicereceives a response message from the slave device, the host deviceconverts the response message into a message which complies with thecommunication protocol of the network device and transmits the convertedmessage to the external network device. The communication protocol ofthe network device may be implemented to be a UPnP communicationprotocol.

Alternatively, when the operation of converting the messages isperformed, the message of the host device and the message of the slavedevice are analyzed and thus converted to correspond to the analyzedresult. The alternative operation has been described above withreference to the message conversion unit 152, and thus detaileddescription will be omitted.

Accordingly, a developer may develop an application in consideration ofonly a single physical connection, and the slave device connected to thehost device may easily be controlled from the outside as the slavedevice connected to the host device operates as a network device.

As described above, according to the method of controlling the slavedevice according to the exemplary embodiment, since the slave deviceconnected to the host device is virtualized to be controlled, the slavedevice connected to the host device may be easily controlled using anexternal device, and a developer may develop an application inconsideration of only a single physical connection. The method ofcontrolling the slave device as shown in FIG. 6 may be applied not onlyto the host device which is configured as shown in FIG. 1 but also imagereading devices having other structures.

Although a few embodiments have been shown and described, it would beappreciated by those skilled in the art that changes may be made in thisembodiment without departing from the principles and spirit of theinvention, the scope of which is defined in the claims and theirequivalents.

1. A host device, comprising: a network communication unit connected toa network; a local communication unit locally connected to a slavedevice; a virtualization unit to virtualize the slave device as anetwork device within the network; and a controlling unit to control thevirtualized slave device as the network device.
 2. The host deviceaccording to claim 1, wherein the virtualization unit comprises: adetermination unit to identify a communication protocol of the slavedevice; a message conversion unit to convert a message of thecontrolling unit into a message which complies with a communicationprotocol of the slave device and a message of the slave device into amessage which complies with a communication protocol of the networkdevice according to the identified communication protocol; and a messagetransmission unit to transmit the message converted by the messageconversion unit to a destination of the message.
 3. The host deviceaccording to claim 2, wherein the message conversion unit analyzes themessage of the controlling unit and the message of the slave device andconverts the messages to correspond to the analyzed result.
 4. The hostdevice according to claim 2, wherein the virtualization unit furthercomprises: an Internet Protocol (IP) address generation unit to allocatean IP address to the slave device when the slave device is connected tothe host device.
 5. The host device according to claim 2, wherein whenthe message of the slave device is received from an external networkdevice connected to the network, the controlling unit controls thevirtualization unit to convert the received message into a message whichcomplies with the communication protocol of the slave device andtransmit the converted message to the slave device.
 6. The host deviceaccording to claim 5, wherein the message transmission unit controls thenetwork communication unit to transmit the converted message of theslave device to the external network device.
 7. The host deviceaccording to claim 2, wherein the communication protocol of the networkdevice is a universal plug-and-play (UPnP) communication protocol. 8.The host device according to claim 1, wherein the slave device isconnected to the host device in at least one of a universal serial bus(USB) communication protocol, an IEEE 1394 communication protocol, aSerial Peripheral Interface (SPI) communication protocol, and aHigh-Definition Multimedia Interface (HDMI) communication protocol.
 9. Amethod to control a slave device locally connected to a host device viaa network, the slave device controlling method comprising: virtualizingthe slave device as a network device within the network; and controllingthe virtualized slave device as the network device.
 10. The slave devicecontrolling method according to claim 9, wherein the virtualizingcomprises: allocating an Internet Protocol (IP) address to the slavedevice when the slave device is connected to the host device; andidentifying a communication protocol of the slave device.
 11. The slavedevice controlling method according to claim 10, wherein the controllingcomprises: converting a message of the host device into a message whichcomplies with a communication protocol of the slave device and a messageof the slave device into a message which complies with a communicationprotocol of the network device, according to the identifiedcommunication protocol; and transmitting the converted message to adestination of the message.
 12. The slave device controlling methodaccording to claim 11, wherein the converting analyzes the message ofthe host device and the message of the slave device and converts themessages to correspond to the analyzed result.
 13. The slave devicecontrolling method according to claim 9, wherein when the message of theslave device is received from an external network device connected tothe network, the controlling converts the received message into amessage which complies with the communication protocol of the slavedevice and transmits the converted message to the slave device.
 14. Theslave device controlling method according to claim 13, wherein thecontrolling transmits the converted message of the slave device to theexternal network device.
 15. The slave device controlling methodaccording to claim 10, wherein the communication protocol of the networkdevice is a universal plug-and-play (UPnP) communication protocol. 16.The slave device controlling method according to claim 9, wherein theslave device is connected to the host device in at least one of auniversal serial bus (USB) communication protocol, an IEEE 1394communication protocol, a Serial Peripheral Interface (SPI)communication protocol, and a High-Definition Multimedia Interface(HDMI) communication protocol.
 17. A slave device controlling method,comprising: converting a message at a host device connected to the slavedevice via a network from a first communication protocol to a secondcommunication protocol so that the slave device is virtualized as anetwork device of the network.
 18. The slave device controlling methodaccording to claim 17, wherein the first communication protocol is acommunication protocol of the network device and the secondcommunication protocol is a communication protocol of the slave device,and the message is converted from the first communication protocol ofthe network device into the second communication protocol of the slavedevice and transmitted to the slave device.
 19. The slave devicecontrolling method according to claim 17, wherein the firstcommunication protocol is a communication protocol of the slave deviceand the second communication protocol is a communication protocol of thenetwork device, and the message is received from the slave device andconverted from the first communication protocol of the slave device intothe second communication protocol of the network device.
 20. The slavedevice controlling method according to claim 17, wherein the host devicereceives the message from an external network device, converts themessage from a first communication protocol of the external networkdevice into a second communication protocol of the slave device andtransmits the converted message to the slave device.